防灾减灾工程学报2025，Vol.45Issue(6)：1311-1370,60.DOI:10.13409/j.cnki.jdpme.20250501002
砂土液化不变性理论
Invariance Theory of Sand Liquefaction under Cyclic Loadings
摘要
Abstract
Due to the uncertainties in seismic motions and storm waves,the diversity of liquefiable soils,and the complexity of sand liquefaction mechanisms,fundamental issues such as fundamental physico-mechanical mechanisms behind excess pore water pressure(ue)generation in a liquefiable soil,the collective effects of multifactorial interactions on ue generation,and liquefaction triggering criteria remain unclear.Based on decades of studies,Chen et al.proposed an invariance theory of sand lique-faction,incorporating invariant state thresholds and intrinsic laws governing cyclic behavior and solid-liquid phase-transitions,which lead to a universal paradigm for site liquefaction evaluation rooted in in-variant physical and mechanical correlations.This novel theory of sand liquefaction mainly includes the following four aspects.(1)For a liquefiable soil at a specific initial physical state,the threshold general-ized shear strain is an intrinsic index that distinguishes nonlinear elastic and elastoplastic states,with a constant value.A power-law relationship is observed between cumulative dissipated energy per unit volume(Wc)and generalized shear strain amplitude(γga),reflecting the invariance in constitutive be-havior.(2)The evolution of soil particle-fabric system governs ue generation in liquefiable soils through physico-mechanical mechanisms,with physical state changes serving as the intrinsic mecha-nism driving ue generation.Differences in ue generation rates under various cyclic loadings primarily stem from corresponding differences in shear strain rates.The marginal peak excess pore pressure ratio(ru,pm),marking the transition from a solid-liquid mixed phase to a transiently viscous fluid phase,ex-hibits dual invariance in mechanics and physics.A ru,pm value of 0.90 can be used as a liquefaction trig-gering criterion for soils both in laboratory element tests and field conditions.The relationship between USR(unit cyclic stress ratio)and Nclt(number of cycles required to trigger liquefaction defined by ru,pm=0.90)follows a negative power-law,thereby forming the threshold state line between the solid-liq-uid mixed phase and the liquid phase.This USR-Nclt curve depends solely on the initial state of the soil.(3)The equivalent skeleton void ratio(e*sk)serves as a single-variable proxy for the physical state of granular soils.For soils with fines particle content below a threshold,negative power-laws exist in the correlations between liquefaction resistance(CRR15 or URR15)in 15 cycles and e*sk,and between the stress-corrected shear-wave velocity(Vs1)and e*sk.Based on the principle of mapping transitivity,a unique correspondence between CRR15 and Vs1,i.e.,liquefaction triggering curve,can be established through the index e*sk,indicating a novel and universal paradigm for site liquefaction potential evalua-tion.(4)The generalized shear strain serves as an equivalent shear strain(γeq)proxy for reflecting the 2D and 3D stress-strain state.A shear strain reversal at the irregular stress-strain loops of cycles in the Chen et al.'s generalized non-Masing,nonlinear,and hysteretic constitutive model of soil will occur when the incremental shear strain Δγeq=0.This strain reversal criterion is independent of the stress-strain hysteretic paths.The physical correlation between the maximum shear modulus and the extreme(maximum and minimum)void ratios exhibits an invariant mathematical form.Equivalent secant shear modulus and damping ratio across a wide strain range can be calculated through the shear stress/strain autocorrelation/cross-correlation functions,with algorithms invariant in mathematical form and physi-cal mechanism.The physics-based model for the peak pore pressure increment(Δuep)demonstrates tri-ple invariance in constitutive behavior,mathematical form,and cyclic loading conditions.A universal correlation links the peak pore pressure ratio(rup)to γga.The coupling of the Chen et al.'s non-Masing constitutive model and the Chen et al.'s Δuep model yields a novel effective stress-strain constitutive model of soil.Consequently,two novel universal site liquefaction potential evaluation methods are es-tablished:a total stress method(rup model-based)and an effective stress method(Δuep model-based).The invariance theory provides a unified basis for refining liquefaction mechanisms,improving evalua-tion methodologies,and advancing mitigation strategies in geotechnical earthquake engineering.The insights derived from decades of research,as reported in this study,will potentially enable the scientif-ic and engineering communities to reinterpret the liquefaction mechanism,its evaluation paradigms,and liquefaction mitigation strategies.关键词
砂土液化/不变性理论/液化机理/固-液相变/液化触发准则/等效状态理论/场地液化评价范式Key words
sand liquefaction/invariance theory/liquefaction mechanism/solid-liquid phase transition/liquefaction triggering criterion/equivalent state theory/site liquefaction evaluation para-digm分类
建筑与水利引用本文复制引用
CHEN Guoxing,WU Qi,Charng Hsein JUANG..砂土液化不变性理论[J].防灾减灾工程学报,2025,45(6):1311-1370,60.基金项目
国家自然科学基金项目(52278503,52378346)资助 （52278503,52378346）
